When we purchased our sienna we made sure to get the updated map disk. When we go on trips, the NAV system seems to use the close your eyes, throw a dart and select the street to drive on method of routing. Recently we went on a trip that was all interstates, and the NAV system took us on back roads the entire way. I tried to select the main roads, but it would take us to the back roads again. If we had followed the NAV directions the 3 hour trip would have taken 7 or more. I feel that I must be missing something. Are there some settings I can change to make the NAV system useful for more than a map book?